1. Field of the Invention
The present invention relates to a multi-display control system for controlling an image signal generator and an image display apparatus, and more specifically relates to a multi-display control system and an image display apparatus, which control an image signal generator having a predetermined format used for example in a personal computer or a work station, and an image display apparatus configured to contain a display device such as a liquid crystal, a CRT, or a plasma display (PDP), and also perform image display control when multiple units of said image display apparatus are connected to said image signal generator.
2. Description of the Related Art
For example, in Japanese Unexamined Patent Application, First Publication No. 2001-67055 and the like, an image display apparatus is disclosed which can display images in multiple displays by interchanging various input signals with each other. FIG. 9 is a block diagram of a multi-display control system which controls displays, used in the image display apparatus disclosed in Japanese Unexamined Patent Application, First Publication No. 2001-67055. In this figure, a two input-type display apparatus 10 and a two input-type display apparatus 20 are connected to each other by a signal line 30.
A signal A is input to a connector 11 of the two input-type display apparatus 10, and in the same way a signal D is input to a connector 22 of the two input-type display apparatus 20. Moreover, a connector 12 and a connector 21 which are not in use, are connected to each other. In the display apparatus 10, when the user operates an interchange switch 16 to select the connector 11, the selector 14 connects the connector 11 to a display 15. As a result, the display 15 displays the image corresponding to the signal A. Also, when the user selects the connector 12 by means of the interchange switch 16, the selector 14 connects the connector 12 to the display 15. Moreover, that selection signal operates a selector 23 via the connector 12 and the connector 21. As a result, the selector 23 connects the connector 22 and the connector 21. This time, because the connector 12 and the connector 21 are already connected, as a result the display 15 can display the image corresponding to the signal D input to the connector 22. Also in the display apparatus 20, by operating the interchange switch 26, the operation can be performed in the same way as above. As a result, because the various signals input to the display apparatuses 10 and 20 can be interchanged with each other and displayed, a very effective supply of information can be performed during explanations and presentations and so on to customers.
Also, in Japanese Unexamined Patent Application, First Publication No. 2000-352962, a technique is disclosed in which a frame is selected to display an image, by using an index image signal for discriminating an image display apparatus, to discriminate an index. According to this technique, even if the number of display apparatuses increases, there is no increase in the number of connection cables and image signal generators for generating image signals. FIG. 10 is a block diagram of an index-type multi-display system as disclosed in Japanese Unexamined Patent Application, First Publication No. 2000-352962. In FIG. 10, multiple image display apparatuses 32 configured containing display devices such as liquid crystal panel, CRT, or plasma display (PDP) and the like, are connected to an image signal generator 31 which generates image signals having a predetermined format used in personal computers and work stations and so on. In the figure, each image display apparatus 32 has been given a different image display apparatus number 31, 32, to 3n. 
The image signal generator 31 outputs as a composite signal; a net image signal which is actually displayed in the image display section of the liquid crystal panel or the like provided in the image display apparatus 32, a similar signal which corresponds to this net image signal, and a transmission index signal substituted for one part of the net image signal. The composite signal output from the image signal generator 31 is transmitted in parallel to the multiple connected image display apparatuses 32. The multiple image display apparatuses 32 comparison check the pre-allocated image display apparatus numbers with the transmission index signal, and only the conformed net image signal is displayed in the image display section of the appropriate image display apparatus 32. As a result, there is no increase in the number of image signal generating devices and connection cables, and arbitrary image can be displayed on any image display apparatus.
Furthermore, recently, because operating systems (OS) such as Windows (registered trademark) are supporting multi-display, multi-display applications have become fairly widespread. However, in the conventional multi-display described above, even if the image display process is performed as a hypothetical single-sheet page, the image actually displayed by the application is displayed separately on various different display apparatuses.
FIG. 1 is a conceptual view showing an operation of a conventional multi-display system, showing a state in which a hypothetical single-sheet page image is displayed separately on multiple image display apparatuses. As shown in FIG. 1, even when processed as a hypothetical single-sheet page 5 within the computer, the display actually displayed by the application is fixed, and due to performing operations by displaying multiple applications on the screens of multiple image display apparatuses 32, when the application in use changes, the display in use (that is, the image display apparatus 32) changes also. Therefore, a working space depending on the application in use is not displayed on the image display apparatus 32 which faces to an operator, and it becomes necessary for the operator to move in front of each image display apparatus 32. Also, in the multi-display control system of the image display apparatus disclosed in Japanese Unexamined Patent Application, First Publication No. 2001-67055, it is necessary for the user to operate a switch to interchange the display, and when three or more display apparatuses are being used, it is necessary to provide the connector for each displays, and the connection cables increase and also the multi-display control system becomes complicated.
The present invention takes the above problems into consideration, with the object of providing a multi-display control system with improved image display operating efficiency, which in a state where the multi-display is in use, the operation screen will come up on the operator's front screen even in the case where the application performing the operation changes, and it is not necessary for the operator to move the display image.